US5676321A - Cutting disk - Google Patents

Abstract

A cylindrical cutting disk for use in a shredder having a plurality of circumferentially spaced teeth, each tooth having a tapered and angled cutting edge. In a preferred embodiment, the disk includes a spacer located on one side of the disk, the spacer having a smooth outer surface and an inner lining coextensive with the lining of the central aperture of the disk. A plurality of disks may be mounted on a cutting cylinder. The disk can be made by sintering.

Description

BACKGROUND OF THE INVENTION

This invention relates to a cutting disk for use in a shredder and the method of making the disk.

Generally, there are two types of cutting mechanisms, "straight cut" or "strip" and "cross cut." A "straight cut" shredder cuts the paper into long, thin strips of paper. This result may be undesirable because the long thin strips make it possible to reassemble the original documents.

A "cross cut" shredder, on the other hand, generally comprises a pair of parallel cutting cylinders that contain a series of offset cutting disks arranged along the axis of the cylinders. Cross cut shredders produce small paper chips. Although this result is more desirable, the current designs are problematic. Cross cut cylinders machined from solid steel or individual machine cutters must be made from hardened material or must be hardened after machining to be strong enough to withstand the staples and paperclips, which will inevitably be put into the shredder along with paper. All of these options are expensive. Individual cutters with the cutting edges extending beyond the perimeter of the cutter have been made inexpensively of sintered or stamped metal, but these cutters require more power and are louder than cross cut cutters whose cutting edges do not protrude beyond the perimeter of the disk.

A cross cut cutting cylinder containing inexpensive cutting disks that enable a low noise, low power shredder to efficiently cut paper would be a welcome improvement in the art.

SUMMARY OF THE INVENTION

The invention provides a cutting disk having a plurality of circumferentially spaced teeth that do not protrude past the perimeter of the disk, each tooth having a cutting edge, each cutting edge being tapered and angled in the same direction as the cutting edges of the other teeth. In the preferred embodiment, the disk also includes a spacer located on one side of the disk, the spacer having a smooth outer surface and an inner lining that is coextensive with the lining of the central aperture of the disk.

The invention also includes a cutting cylinder having a hexagonal shaft and a plurality of cutting disks mounted on the shaft, each cutting disk having a plurality of circumferentially spaced teeth that do not protrude past the perimeter of the disk, each tooth having a cutting edge, each cutting edge being tapered and angled in the same direction as the cutting edges of the other teeth, and a central aperture for placing the disk on the shaft.

In addition, the present invention encompasses a shredder having two parallel cutting cylinders, each cylinder having a hexagonal shaft and a plurality of spaced apart cutting disks with the cutting disks of the first cutting cylinder interleaved with the cutting disks of the second cutting cylinder, each cutting disk having a plurality of circumferentially spaced teeth that do not protrude past the perimeter of the disk, each tooth having a cutting edge that is tapered and angled, each cutting edge being tapered and angled in the same direction as the other teeth, and a central aperture for placing the disk on the shaft.

The invention further includes the method of making the above-described cutting disk by molding and sintering.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of the preferred cutting disk.

FIG. 2 is an exploded view of a portion of a cutting cylinder containing a plurality of the cutting disks of FIG. 1.

FIG. 3 is a front view of the cutting disk of FIG. 1.

FIG. 4 is an enlarged view of the cutting edge of the teeth on the cutting disk of FIG. 1.

FIG. 5 is a perspective view of a portion of a dual cylinder arrangement containing the cutting disks of FIG. 1.

FIG. 6 is an enlarged view of the tapered cutting edge of the teeth on the cutting disk of FIG. 1.

DETAILED DESCRIPTION OF THE DRAWINGS AND PREFERRED EMBODIMENTS OF THE INVENTION

FIG. 1 shows the preferred embodiment of thecutting disk 10 of the present invention. As illustrated, thecutting disk 10 is cylindrical and includes a plurality of circumferentially spaced teeth 20 that do not protrude past the perimeter of the disk. Thepreferred disk 10 has four teeth 20 positioned ninety degrees from one another. Each tooth 20 has a cutting edge 21 that is tapered on the top and angled. Tapering and angling the cutting edge 21 provides a sharp surface which can easily penetrate the material that is to be shredded. As clearly shown in FIG. 4, the cutting edge 21 is preferably tapered to anangle 22 in the range of 20 to 45 degrees, more preferably 25 to 40 degrees, and most preferably 35 degrees. The curing edge 21 is preferably angled 23 in the range of 20 to 90 degrees, more preferably 30 to 75 degrees, and most preferably 45 degrees.

In the preferred embodiment, the cutting edge 21 of each tooth 20 is tapered 22 and angled 23 in the same direction as the cutting edges 21 of the other teeth 20. The teeth 20 on thecutting disk 10 are separated by a plurality of circumferentially spacedgullets 30. In the preferred embodiment, there are an equal number of teeth 20 andgullets 30. Thecutting surface 24 of thedisk 10 may extend from the cutting edge 21 to the beginning of thenext gullet 30.

Thedisk 10 also has acentral aperture 40 which enables thedisk 10 to be placed on a shaft 50. Theaperture 40 is lined with a plurality ofserrations 41. Theserrations 41 allow thedisk 10 to be offset along the shaft 50 of acutting cylinder 60 and thus provide a means of offsettingindividual disks 10 with respect to each other. In the preferred embodiment, there are eighteenserrations 41.

As illustrated in FIG. 3, the preferred embodiment of thecutting disk 10 includes aspacer 70 located on one side of thedisk 10. Thespacer 70 has a smooth outer surface and an inner lining that is coextensive with the lining of thecentral aperture 40. Preferably thespacer 70 is integral with the body of the disk. Alternately, thespacer 70 may be a separate component which provides distance betweenindividual disks 10 on acutting cylinder 60. If thespacer 70 is a separate component, it is preferably attached or affixed to the body of thedisk 10. Any method of attachment presently known in the art is appropriate. When thedisks 10 are used in a dual cylinder shredding machine, thedisks 10 are arranged in an interleaving pattern which will be further described hereafter. Thus,disks 10 on onecylinder 60a must be positioned so that adisk 10 from anothercylinder 60b could be positioned between them. Therefore, although the actual size of thespacer 70 is not critical, thespacer 70 must be slightly wider than anindividual disk 10.

FIG. 2 depicts a cuttingcylinder 60 containing a plurality of thecutting disks 10 of the present invention. As illustrated, thecutting cylinder 60 has a shaft 50 upon which thecutting disks 10 are mounted. In the preferred embodiment, the shaft 50 has a hexagonal cross-section. Thecutting disks 10 are somewhat reciprocally displaced, or indexed, in the longitudinal direction of thecutting cylinder 60 so that a large pitch helix is formed on the surface. The helical displacement insures that the engagement of the teeth 20 into the paper to be shredded is gentle and takes place continuously along the longitudinal direction of thecutting cylinder 60. The reciprocal displacement betweendisks 10 on thecutting cylinder 60 may vary in several respects. First, the amount or degree of displacement may vary. Preferably, the reciprocal displacement is not more than a fraction of an inch or a few millimeters or fractions thereof. In the preferred embodiment, thedisks 10 are staggered by ten degrees. Secondly, thedisks 10 may be staggered individually, as shown in FIG. 2, or in groups of two or more. For example, a group of fourindividual cutting disks 10 may be reciprocally displaced from the adjacent group of fourindividual cutting disks 10. Alternately, a group of two disks may be staggered from the adjacent group of three disks. Any pattern or grouping ofdisks 10 that produces the desired helix is acceptable.

As explained previously, the preferredcutting disk 10 of the present invention has acentral aperture 40 lined with eighteenserrations 41. Although theserrations 41 are twenty degrees each, it is possible to offset thedisks 10 on a hexagonal shaft 50 in ten degree increments as depicted in FIG. 2. More specifically, the relationship between thetip 25 of the cutting edge 21 and theserrations 41 lining theaperture 40 allowdisks 10 to be offset from each other by ten degrees. As best illustrated in FIGS. 1 and 4, eachdisk 10 of the preferred embodiment has asmall indentation 42 in its side wall which marks an initial or starting position for purposes of placing thedisks 10 on a shaft 50. At this initial position, thetip 25 of the cutting edge 21 on the first tooth 20a is lined up with a "peak" 41a in the serrated lining of theaperture 40. On the other hand, thetip 25 of the cutting edge 21 on theteeth 20b and 20d adjacent the first tooth are lined up with "valleys" 41b in the serrated lining. Thetip 25 of the cutting edge 21 on the tooth 20c opposite the first tooth 20a is lined up with a peak 41a. This alternating pattern is critical to achieving a ten degree offset betweenindividual disks 10 on a shaft 50. To explain further, thefirst disk 10 is placed on the shaft 50. If thedisks 10 are to be individually offset with respect to each other, the shaft 50 is rotated one hundred degrees before thenext disk 10 is placed on the shaft 50. If the shaft 50 were only rotated ten degrees, theserrated lining 41 of theaperture 40 would not be flush with the shaft 50 and a twenty degree offset would result. If thedisks 10 are not individually offset, but rather are offset in groups of two or more, the shaft 50 is rotated, as just described, between groupings.

The meshing relationship between the cuttingdisks 10 onopposite cutting cylinders 60 can best be seen in FIG. 5. As shown in FIG. 5, the teeth 20 of adisk 10 on thefirst cutting cylinder 60a will overlap with the cuttingsurface 24 on adisk 10 of thesecond cutting cylinder 60b. In this way, the teeth 20 on thefirst cutting cylinder 60a will alternately engage in the paper with the teeth 20 on thesecond cutting cylinder 60b. Furthermore, as evident in FIG. 5, once the cutting edge 21 of adisk 10 on onecylinder 60a contacts the paper, it remains sandwiched between theadjacent disks 10 on theother cutting cylinder 60b and thus is unexposed until it completes the cutting cycle. This meshing arrangement is important to obtain the cross-cutting action which produces the confetti or small chips instead of kinked strips which can be produced when the proper meshing arrangement is not maintained.

It should be understood that thecutting disk 10 described above can be changed in many ways yet still remain within the scope of the invention. For example, the number or shape of teeth 20 could vary. Another variation may alter the number ofserrations 41 lining theaperture 40, thereby changing the manner of indexing thedisk 10 on the shaft 50.

The present invention also includes the method of making thecutting disk 10. Thecutting disk 10 is produced by a two part process which involves molding and sintering. Firstly, metal powder is molded into the desired shape. Any hard metal powder is suitable. The industry designation for one such powder is FL4607. The metal powder is then placed in a press that has the desired shape. The press holds the metal powder together under high pressure. Thus, the desired shape is produced. Next, the molded metal is sintered. During sintering, the molded metal is heated at a high temperature thereby melding the metal particles together. Sintering produces a very hard, porous cutting disk.

Thecutting disk 10 of the present invention provides many advantages. Thecutting disk 10 enables small paper chips to be produced by a machine that is less noisy than many prior art paper shredders. In addition, the cuttingdisks 10 provide for a more energy efficient shredder because they require less power to accomplish the desired results.

Another advantage lies in the fact that thedisks 10 are produced by sintering. Sintering enables disks of the requisite shape and hardness to be manufactured economically.

Of course, it should be understood that a wide range of changes and modifications can be made to the preferred embodiment described above. It is therefore intended that the foregoing description illustrates rather than limits this invention, and that it is the following claims, including all equivalents, which define this invention.

Claims (25)

What is claimed:

1. A cutting disk comprising a plurality of circumferentially spaced teeth that do not protrude past the perimeter of the disk, each tooth having a tapered perimeter and an angled cutting edge, the perimeter and cutting edge of each tooth being tapered and angled, respectively, in the same direction as the perimeters and cutting edges of the other teeth.

2. The cutting disk recited in claim 1 wherein there are four teeth.

3. The cutting disk recited in claim 1 further comprising a central aperture lined with a plurality of serrations.

4. The cutting disk recited in claim 3 wherein there are eighteen serrations.

5. The cutting disk recited in claim 1 wherein the perimeter of each tooth is tapered to an angle in the range of 20 to 45 degrees.

6. The cutting disk recited in claim 1 wherein the cutting edge of each tooth is angled in the range of 20 to 90 degrees.

7. The cutting disk recited in claim 1 further comprising a spacer located on one side of the disk, the spacer having a smooth outer surface and an inner lining that is coextensive with the lining of the central aperture.

8. The cutting disk of claim 7 wherein the inner lining has eighteen serrations.

9. The cutting disk recited in claim 1 wherein the cutting disk is made out of sintered metal.

10. A cutting disk for use in a shredder comprising:

a) four circumferentially spaced teeth that do not protrude past the perimeter of the disk, each tooth having a tapered perimeter and an angled cutting edge, the perimeter and cutting edge of each tooth being tapered and angled, respectively, in the same direction as the perimeters and cutting edges of the other teeth;

b) a central aperture lined with eighteen serrations; and

c) a spacer located on one side of the disk, the spacer having a smooth outer surface and a serrated inner lining that is coextensive with the lining of the central aperture.

11. The cutting disk recited in claim 10 wherein the perimeter of each tooth is tapered to an angle in the range of 20 to 45 degrees.

12. The cutting disk recited in claim 10 wherein the cutting edge of each tooth is angled in the range of 20 to 90 degrees.

13. The cutting disk recited in claim 10 wherein the cutting disk is made out of sintered metal.

14. A cutting cylinder for a shredder comprising:

a) a hexagonal shaft; and

b) a plurality of cutting disks mounted on the shaft, each cutting disk comprising:

i) a plurality of circumferentially spaced teeth that do not protrude past the perimeter of the disk, each tooth having a tapered perimeter and an angled cutting edge, the perimeter and cutting edge of each tooth being tapered and angled, respectively, in the same direction as the perimeters and cutting edges of the other teeth; and

ii) a central aperture for placing the disk on the shaft.

15. The cutting cylinder recited in claim 14 wherein the perimeter of each tooth is tapered to an angle in the range of 20 to 45 degrees.

16. The cutting cylinder recited in claim 14 wherein the cutting edge of each tooth is angled in the range of 20 to 90 degrees.

17. The cutting cylinder recited in claim 14 wherein the central aperture is lined with a plurality of serrations.

18. The cutting cylinder recited in claim 17 wherein the lining has eighteen serrations.

19. The cutting cylinder recited in claim 14 further comprising a spacer located on one side of the disk, the spacer having a smooth outer surface and an inner lining that is coextensive with the lining of the central aperture.

20. The cutting cylinder recited in claim 19 wherein the inner lining has eighteen serrations.

21. The cutting cylinder recited in claim 14 wherein the disks are individually offset with respect to each other.

22. The cutting cylinder recited in claim 14 wherein the disks are offset in ten degree increments.

23. The cutting cylinder recited in claim 14 wherein the disks are offset in groups of two or more.

24. The cutting cylinder recited in claim 23 wherein the disks are offset in ten degree increments.

25. A shredder comprising two parallel cutting cylinders, each cylinder having a hexagonal shaft and a plurality of spaced apart cutting disks with the cutting disks of the first cutting cylinder interleaved with the cutting disks of the second cutting cylinder, each cutting disk comprising:

a) four circumferentially spaced teeth that do not protrude past the perimeter of the disk, each tooth having a tapered perimeter and an angled cutting edge, the perimeter and cutting edge of each tooth being tapered and angled, respectively, in the same direction as the perimeters and cutting edges of the other teeth; and

b) a central aperture for placing the disk on the shaft.

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